Mercury XR2 150 stuggling to get on plane.

[llyons]

Hi Recently in the last 3-4 times out on the boat, the Merc 150xr2 doesnt have the hole shot it used to. It does get on plane but takes about 300 yards and once its on plane it gets going like it used too at WOT. There is no miss. The fuel lines from motor to fuel tank were all changed and the fuel tanks drained and new fuel added. The priming bulb does not seem to get hard but on plane at WOT, it does not have any sputter from a fuel shortage.

I checked the timing for throttle pickup and it was 11deg ATDC and at WOT it was 23 BTDC. This seems to be correct. i also adjusted the carburetor linkages to set the roller against the throttle cam.

i did not rebuild the carbs but did a year ago. I did clean the 6 main jets on the bowls.

What could be causing the motor to not have the hole shot it used too but still achieve the same top end after getting on plane?

 

[Faztbullet]

Water logged, not running on all cylinders,ignition or fuel problems

 

[redneck joe]

I'll vote out waterlogged if it happened suddenly.

Missing a cylinder would be first guess

 

[llyons]

I'll vote out waterlogged if it happened suddenly.

Missing a cylinder would be first guess

Yeah there was no water logging and I did drain the gas tanks.

It does get on plane but very slow.

I am starting to feel like this might be a stator problem. I recall having something like this before but back then I also lost a powerpack / switch box and only had one bank firing. I do have both sides firing but not able to take it into the higher rpm range.


Could a defective high rpm winding on the stator cause this kind of issue?

Would I still be able to get on a plane with the high winding defective?

 

[Chris1956]

Check the fuel pump diaghram. If it leaks, it can load up a cylinder or two at idle. It takes a bit of revving to clear the fouling.

I bad high speed stator winding means no RPM faster than about 2200RPM.

 

[llyons]

Check the fuel pump diaghram. If it leaks, it can load up a cylinder or two at idle. It takes a bit of revving to clear the fouling.

I bad high speed stator winding means no RPM faster than about 2200RPM.

Thanks Chris

I took it out to the water yesterday and 6 times it was able to get on plane and I trimmed it for full WOT for about a quarter mile. Rinse Repeat 6 times. Everything it was slow slow to get on plane.

if I was able to get on plane and noticed 4500 rpms while on plane then there a good chance that the high speed stator windings are ok?

 

[llyons]

BTW, I also measured compression and the values all look really good for such an old motor.

1 123
2 124
3 125
4 127
5 123
6 125

 

[redneck joe]

Yeah those look nice. Have you checked spark at each?

 

[llyons]

Yeah those look nice. Have you checked spark at each?

Yes, I used a timing light on each spark plug wire to confirm.

Also once on plane, I can trim it up and it gets up to 4500 rpm with no problem.

 

[redneck joe]

Is that 4500 in WOT specs? I'm and old 2 stroke dude....

 

[llyons]

Is that 4500 in WOT specs? I'm and old 2 stroke dude....

It was WOT (as fast as I could go). I suspect it can get higher for this motor xr2 (5500-6000).

my question is does getting on plane and getting up to 4500 rpm remove the stator as the problem?

 

[redneck joe]

I dont know much about stators but per the previous post you wouldnt be over 2000 rpm if it was the high thingie on the stator.

Stupid question, you didnt change props did you?

 

[llyons]

Hi

I dont know much about stators but per the previous post you wouldnt be over 2000 rpm if it was the high thingie on the stator.

Stupid question, you didnt change props did you?

No nothing changed like that.

 

[QBhoy]

I’d be looking towards the battery and its charging system. Put a meter across the battery when on trial. Obviously a 2 man job. Having one of these myself…I also know that the main fuse carrier on mine was less than ideal for intermittent contact and poor continuity too.

 

[Chris1956]

Gee, you get 4500 RPM. Anything above 2200 means the high speed stator is working. Did you check the fuel pump diaghram? If it leaks it floods some cylinders causing you to start accelerating on 5 or 4 cylinders. If this is happening, does it sound like it might struggle to accelerate?
Motor full throttle is likely 5500, however I have not looked it up. You should.

 

[Chris1956]

I doubt your charging system is an issue. However, disconnect and insulate the yellow stator wires from the rectifier or voltage regulator.

 

[llyons]

I went through and performed all the stator tests a idle at least.

all the imedance/resistance tests for this CDI stator are within spec.

I also did some DVA tests on at least the blue lines to ground and had 170-180 at idle and increasing with Throttle. ( i just had the DVM with a peak hold)

I verified that the trigger was also in spec and moved freely moving the throttle lever to WOT.

I have not done anything with carbs or fuel pump.

I disconnected the stator charging yellow wires and will test it on water.

I dont think there is a shortage or fuel or it would cut out while on plane and pushing it.

I do notice that the priming bulb does not get hard and in the past i remember this getting pretty firm. Could this indicate some leak? I dont see any gas leaking anywhere?

 

[Dukedog]

I do notice that the priming bulb does not get hard and in the past i remember this getting pretty firm. Could this indicate some leak? I dont see any gas leaking anywhere?

thats a tell tale for fuel delivery.. possible justa the bulb but probably gonna be tha mech pump........ jmo.

 

[jimmbo]

You said in your Original Post "once its on plane it gets going like it used too at WOT"
Then later you say your top Rpm is 4500.
So has 4500 Rpm always been the fastest the engine has ran?

 

[racerone]

There is an issue.---Check the reed valves.----Does spark jump a gap of 3/8" on each lead , yes or no ?-------Use a strong flashlight and look into carburetor bores at full throttle.----Compare fuel coming up the main nozzles.-----And the bulb MUST go hard when filling the carburetors.-----Bulb does not need to be hard when engine is running.-----So find the leak.